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Saw Blade Kerf... What am I missing? Ugh!

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Forum topic by Ray D posted 11-21-2015 04:07 AM 941 views 0 times favorited 8 replies Add to Favorites Watch
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Ray D

17 posts in 659 days


11-21-2015 04:07 AM

Topic tags/keywords: saw blades tablesaw blade table saw blade kerf riving knife splitter blades forrest freud question

Hello,

I’ve read the postings for a few years now but it was only earlier this year that I became a member and since then I have learned so much from all of you… Thank you! Just a bit about myself… it was back in the 70’s (sixth grade) when I pushed my first piece of wood passed a table saw blade (school had a full wood shop). I spent many hours in that shop and found myself spending even more time in my HS shop… all while being guided by some wonderful shop teachers. Since that time I spent many hours in and out of a shop with some being more than others but nothing being truly committed. However, it wasn’t until the last year or so, when I became sick did I begin putting a shop back together. I have a lot of time on my hands now-a-days and what better way to spend it but to spend it doing something I have always loved. Anyway, I have some catching up to do with all the fancy accessories, some I have read about, many I have and others are just so silly or confusing I’m not sure which way is up. Table saw blades being one of them. With limited space left in a finished basement and with the other full size shop tools, I only had room for a contractors saw (DeWalt 7499) that I built into a cabinet/bench.

I have read what I believe to be everything (LOL) there is on this site about saw blades so if I missed a previous post that answers my question, please forgive. Why is it saw blades are stamped (or reported) with the kerf in fraction and decimal with neither of them matching in size. Example is Freud Premier Fusion General Purpose Blade show a kerf of 3/32 and .091. Knowing that 3/32 is .09375 or as some say .094. I presented this question to Freud and got an answer of “3/32” is the fractional equivalent of .093 which means it is only two thousands of an inch different from .091 (virtually the same size)”. I ask this question because my saws riving knife says to use a min. of .094 kerf blade. I may not be feeling well or maybe I am overthink it but that three thousands of an inch could be trouble? I think WW II does the same thing with their markings. Can someone please help? I just need a VERY GOOD thin kerf blade or two separate blades. It doesn’t matter which way. UGH! Maybe I should just heat the garage, build a shop out there and buy a bigger saw. Ha!

Thanks,
Ray

-- Ray - Minooka, Illinois


8 replies so far

View runswithscissors's profile

runswithscissors

2192 posts in 1493 days


#1 posted 11-21-2015 05:34 AM

I wouldn’t worry about what it says on the riving knife. Instead, a quick way to tell whether there could be a problem is to remove the riving knife, run a short cut (2” or so) into the end of a piece of wood, then see whether the riving knife will accept the wood with that cut width. If it binds or sticks, then you have a problem. My guess is that it will be okay. If the kerf is a little wide (the blade can wiggle in the cut), I would have no concern about that. The main point of a RK is to prevent the wood from contacting the back of the blade as it passes by. That’s what leads to a kickback. The other function of a RK is to prevent reaction wood from pinching the blade as it leaves the blade, also a potential kick back scenario.

When I first put a RK on my older Unisaw, I was using a TK blade—also a Freud Diablo. I took the wood down to the steel yard with a kerf sawn in it, and found that it fit 14 gauge perfectly. No slop, no binding. No worry about .0002” of anything. One of the first cuts I did was with some oak with a lot of built in wonkiness, and it pinched the RK so firmly that I couldn’t advance it any further. Made me glad it was there.

-- I admit to being an adrenaline junky; fortunately, I'm very easily frightened

View Rick M's profile

Rick M

7935 posts in 1848 days


#2 posted 11-21-2015 06:32 AM

Because 91/1000 doesn’t simplify but the closest fraction is 3/32”. The difference between the two is approximately half the thickness of a sheet of copy paper; insignificant to woodworking.

-- http://thewoodknack.blogspot.com/

View Mark Kornell's profile

Mark Kornell

1061 posts in 1998 days


#3 posted 11-21-2015 07:10 AM

Ray, welcome to LumberJocks!

Sorry to hear that you are (have been?) ill. And here’s hoping that if you aren’t already on the mend, that you soon will be. A serious illness is what brought me to woodworking – the cancer has been left behind but it is full steam ahead with the woodworking.

The key thing is that the blade has a kerf that is larger than the riving knife. If the manufacturer specs the kerf in a decimal number, that is more accurate than a fraction so go by the decimal number. If you have a caliper that indicates thousandths, use that to get an accurate measurement of your riving knife. Any blade which has an equal or larger kerf than that number will work.

As runswithscissors says, you can do an easy check without a caliper by removing the riving knife, making a test cutand then checking to see if the riving knife will fit in the kerf.

-- Mark Kornell, Kornell Wood Design

View rwe2156's profile

rwe2156

2200 posts in 948 days


#4 posted 11-21-2015 10:47 PM

If the riving knife is a couple thou narrower than the kerf, I don’t think that will be a problem.
You should still be able to push the wood through easily.

-- Everything is a prototype thats why its one of a kind!!

View knotscott's profile

knotscott

7225 posts in 2843 days


#5 posted 11-21-2015 11:24 PM

As mentioned previously, the important thing is that the total kerf be at least as wide as the riving knife. Keep in mind that the actual overall kerf width of the blade is the width of the teeth, plus the combined runout of the arbor and blade while in motion, which will always be a tad wider than the actual tooth width. IMO it’s better to error on the safe side, so I’d aim more towards the 3/32” TK blades with a stated width of a bit more than 0.094” if possible. The narrower Freud blades “might” be fine, but there are enough other comparable choices that there’s really no reason to chance it.

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-- Happiness is like wetting your pants...everyone can see it, but only you can feel the warmth....

View runswithscissors's profile

runswithscissors

2192 posts in 1493 days


#6 posted 11-21-2015 11:52 PM

Do the RKs that are included with table saws come in any thicknesses other than full kerf and thin kerf? I can’t imagine the manufacturers would make an RK that would not work for any and all blades available within either of those two size designations. In other words, I think this is a non-issue, and there is no need whatsoever to “err on the safe side.”

Admittedly, I do sometimes see posts on here where people are grinding or sanding their RKs thinner to make them work, but I think something else may be going on there—namely that they are trying to use a TK blade with a FK riving knife.

-- I admit to being an adrenaline junky; fortunately, I'm very easily frightened

View alittleoff's profile

alittleoff

296 posts in 744 days


#7 posted 11-22-2015 12:27 AM

My saw came with a thick kerf riving knife. I had the same question about it, and got about the same answers that have been posted here. What I did was make sure the riving knife was dead center, or as close as I could get it to the blade. I haven’t had any problems with a thin kerf blade at all. Also the saw came with a thin kerf blade. Hope I got the thick and thin of this correct. Kind of confusing.
Gerald

View Ray D's profile

Ray D

17 posts in 659 days


#8 posted 11-22-2015 06:49 PM

Thanks all! I guess I was over thinking it and needed the guidance from those with more experience. I have narrowed it down to the TK WW II or the LU87R010 and a good crosscut which I’m still looking for. From what I’ve read, I tend to think a two blade process will be the way to go. Thanks again for the wonderful guidance.

-- Ray - Minooka, Illinois

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